Physiology and Pharmacology PublicationsCopyright (c) 2015 Western University All rights reserved.http://ir.lib.uwo.ca/physpharmpub
Recent documents in Physiology and Pharmacology Publicationsen-usFri, 31 Jul 2015 19:29:15 PDT3600HIGHER HEPATIC MIR-29 EXPRESSION IN UNDERNOURISHED MALE RATS DURING THE POSTNATAL PERIOD TARGETS THE LONG-TERM REPRESSION OF INSULIN-LIKE GROWTH FACTOR 1http://ir.lib.uwo.ca/physpharmpub/96
http://ir.lib.uwo.ca/physpharmpub/96Fri, 10 Jul 2015 11:33:37 PDT
A nutritional mismatch in postnatal life of low birth weight offspring increases the risk of developing the metabolic syndrome. Moreover, this is associated with decreased hepatic insulin-like growth factor 1 (Igf1) expression, leading to impaired growth and metabolism. Previously we have demonstrated that the timing of nutritional restoration in perinatal life can differentially programhepatic gene expression. While micro RNAs also play an important role in silencing gene expression, to date, the impact of a nutritional mismatch in neonatal life on their long-term expression has not been evaluated. Given the complementarity of miR-29 to the 3i-UTR of Igf1, we examined how proteins restoration in maternal protein restricted rat (MPR) offspring influences hepatic miR-29 and Igf1 expression in adulthood. Pregnant Wistar rats were designated into one of four dietary regimes; 20% protein (Control), 8% protein during lactation only (LP-Lact), 8% protein during gestation only (LP1) or both (LP2). The steady-state expression of hepatic miR-29 mRNA significantly increased in LP2 offspring at postnatal day 21 and 130 and this was inversely related tohepatic Igf1 mRNA and body weight. Interestingly, this reciprocal association was stronger inLP-Lact offspring at postnatal day 21. Functional relevance of this in vivo relationship was evaluated by transfection of miR-29 mimics in neonatal clone 9 rat hepatoma cells. Transfection with miR-29suppressed Igf1 expression by 12 hours. Collectively, these findings implicate that nutritional restoration post-weaning (after liver differentiation) in MPR rat offspring fails to prevent long-term impaired growth, in part, due to miR-29 suppression of hepatic Igf1 expression.
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Gurjeev Sohi et al.Maternal Nicotine Exposure Leads to Impaired Disulfide Bond Formation and Augmented Endoplasmic Reticulum Stress in the Rat Placentahttp://ir.lib.uwo.ca/physpharmpub/95
http://ir.lib.uwo.ca/physpharmpub/95Sat, 28 Mar 2015 08:19:17 PDT
Maternal nicotine exposure has been associated with many adverse fetal and placental outcomes. Although underlying mechanisms remain elusive, recent studies have identified that augmented endoplasmic reticulum (ER) stress is linked to placental insufficiency. Moreover, ER function depends on proper disulfide bond formation-a partially oxygen-dependent process mediated by protein disulfide isomerase (PDI) and ER oxidoreductases. Given that nicotine compromised placental development in the rat, and placental insufficiency has been associated with poor disulfide bond formation and ER stress, we hypothesized that maternal nicotine exposure leads to both placental ER stress and impaired disulfide bond formation. To test this hypothesis, female Wistar rats received daily subcutaneous injections of either saline (vehicle) or nicotine bitartrate (1 mg/kg) for 14 days prior to mating and during pregnancy. Placentas were harvested on embryonic day 15 for analysis. Protein and mRNA expression of markers involved in ER stress (e.g., phosphorylated eIF2α, Grp78, Atf4, and CHOP), disulfide bond formation (e.g., PDI, QSOX1, VKORC1), hypoxia (Hif1α), and amino acid deprivation (GCN2) were quantified via Western blot and/or Real-time PCR. Maternal nicotine exposure led to increased expression of Grp78, phosphorylated eIF2α, Atf4, and CHOP (p
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Michael Wong et al.Deep brain stimulation of the medial septum or nucleus accumbens alleviates psychosis-relevant behavior in ketamine-treated rats.http://ir.lib.uwo.ca/physpharmpub/94
http://ir.lib.uwo.ca/physpharmpub/94Sat, 14 Mar 2015 11:41:25 PDT
Deep brain stimulation (DBS) has been shown to be effective for relief of Parkinson's disease, depression and obsessive-compulsive disorder in humans, but the effect of DBS on psychosis is largely unknown. In previous studies, we showed that inactivation of the medial septum or nucleus accumbens normalized the hyperactive and psychosis-related behaviors induced by psychoactive drugs. We hypothesized that DBS of the medial septum or nucleus accumbens normalizes the ketamine-induced abnormal behaviors and brain activity in freely moving rats. Male Long-Evans rats were subcutaneously injected with ketamine (3 mg/kg) alone, or given ketamine and DBS, or injected with saline alone. Subcutaneous injection of ketamine resulted in loss of gating of hippocampal auditory evoked potentials (AEPs), deficit in prepulse inhibition (PPI) and hyperlocomotion, accompanied by increased hippocampal gamma oscillations of 70-100 Hz. Continuous 130-Hz stimulation of the nucleus accumbens, or 100-Hz burst stimulation of the medial septum (1s on and 5s off) significantly attenuated ketamine-induced PPI deficit and hyperlocomotion. Medial septal stimulation also prevented the loss of gating of hippocampal AEPs and the increase in hippocampal gamma waves induced by ketamine. Neither septal or accumbens DBS alone without ketamine injection affected spontaneous locomotion or PPI. The results suggest that DBS of the medial septum or nucleus accumbens may be an effective method to alleviate psychiatric symptoms of schizophrenia. The effect of medial septal DBS in suppressing both hippocampal gamma oscillations and abnormal behaviors induced by ketamine suggests that hippocampal gamma oscillations are a correlate of disrupted behaviors.
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Jingyi Ma et al.Deep brain stimulation of the medial septum or nucleus accumbens alleviates psychosis-relevant behavior in ketamine-treated rats.http://ir.lib.uwo.ca/physpharmpub/93
http://ir.lib.uwo.ca/physpharmpub/93Fri, 13 Mar 2015 13:37:37 PDT
Deep brain stimulation (DBS) has been shown to be effective for relief of Parkinson's disease, depression and obsessive-compulsive disorder in humans, but the effect of DBS on psychosis is largely unknown. In previous studies, we showed that inactivation of the medial septum or nucleus accumbens normalized the hyperactive and psychosis-related behaviors induced by psychoactive drugs. We hypothesized that DBS of the medial septum or nucleus accumbens normalizes the ketamine-induced abnormal behaviors and brain activity in freely moving rats. Male Long-Evans rats were subcutaneously injected with ketamine (3 mg/kg) alone, or given ketamine and DBS, or injected with saline alone. Subcutaneous injection of ketamine resulted in loss of gating of hippocampal auditory evoked potentials (AEPs), deficit in prepulse inhibition (PPI) and hyperlocomotion, accompanied by increased hippocampal gamma oscillations of 70-100 Hz. Continuous 130-Hz stimulation of the nucleus accumbens, or 100-Hz burst stimulation of the medial septum (1s on and 5s off) significantly attenuated ketamine-induced PPI deficit and hyperlocomotion. Medial septal stimulation also prevented the loss of gating of hippocampal AEPs and the increase in hippocampal gamma waves induced by ketamine. Neither septal or accumbens DBS alone without ketamine injection affected spontaneous locomotion or PPI. The results suggest that DBS of the medial septum or nucleus accumbens may be an effective method to alleviate psychiatric symptoms of schizophrenia. The effect of medial septal DBS in suppressing both hippocampal gamma oscillations and abnormal behaviors induced by ketamine suggests that hippocampal gamma oscillations are a correlate of disrupted behaviors.
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Jingyi Ma et al.Medial septal lesion enhances general anesthesia response.http://ir.lib.uwo.ca/physpharmpub/92
http://ir.lib.uwo.ca/physpharmpub/92Fri, 13 Mar 2015 13:37:35 PDT
Electrolytic lesion of the medial septum, a basal forebrain nucleus that projects to the hippocampus, prolonged the emergence from general anesthesia in rats. Septal lesioned rats required a longer time to recover from a loss of righting reflex (LORR) and a loss of tail-pinch response after injectable (20 mg/kg i.p. pentobarbital, 5mg/kg i.v. propofol) or volatile (1.5% halothane, 2% isoflurane) anesthetic. When incremental doses of propofol were given i.p., septal lesioned rats as compared to control rats showed LORR at a lower dose of propofol. Similarly, when the rats were exposed to increasing concentrations of isoflurane, the percent of rats showing LORR was leftward shifted for lesioned rats as compared to control rats. Septal lesioned rats as compared to control rats showed decreased locomotor activity when exposed to 1.5% halothane. Lesion of the medial septum was confirmed by thionin-stained histological sections as well as loss of acetylcholinesterase (AchE) staining in the hippocampus, indicating a depletion of septohippocampal cholinergic afferents. Medial septal lesion resulted in a near complete loss of hippocampal theta rhythm during walking and a general decrease in power of the hippocampal EEG at all frequencies (0-100 Hz), during walking or immobility. It is concluded that lesion of medial septum, in part through a loss of septohippocampal cholinergic afferents, increased the anesthesia response to volatile and injectable general anesthetics, during both induction and emergence. It is suggested that the septohippocampal system participates in many components of general anesthesia including hypnosis, immobility, and analgesia.
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L Stan Leung et al.AcetylcholinesteraseAnesthetics, GeneralAnimalsBrain WavesDose-Response Relationship, DrugElectroencephalographyHippocampusImmobilizationLightMalePain MeasurementRatsRats, Long-EvansReflexSeptum of BrainTheta RhythmTime FactorsWalkingLoss of dendritic inhibition in the hippocampus after repeated early-life hyperthermic seizures in rats.http://ir.lib.uwo.ca/physpharmpub/91
http://ir.lib.uwo.ca/physpharmpub/91Fri, 13 Mar 2015 13:37:32 PDT
Seizures are relatively common in children and are a risk factor for subsequent temporal lobe epilepsy. To investigate whether early-life seizures themselves are detrimental to the proper function of the adult brain, we studied whether dendritic excitation and inhibition in the hippocampus of adult rats were altered after hyperthermia-induced seizures in immature rats. In particular, we hypothesized that apical dendritic inhibition in hippocampal CA1 pyramidal cells would be disrupted following hyperthermia-induced seizures in early life. Seizure rats were given three hyperthermia-induced seizures per day for three days from postnatal day (PND) 13 to 15; control rats were handled similarly but not heated. At PND 65-75, paired-pulse inhibition in area CA1 was evaluated under urethane anesthesia, using CA3 and medial perforant path (MPP) stimulation to excite the proximal and distal apical-dendrites, respectively, and the evoked field potentials were analyzed by current source density. There was no difference in the CA1 response to single-pulse stimulation of CA3 or MPP. In control rats, a high-intensity CA3 stimulus inhibited a subsequent MPP-evoked CA1 distal dendritic excitatory sink, and the inhibition at 150-200 ms was blocked by a GABA(B) receptor antagonist. Seizure as compared to control rats showed a decrease in a CA3-evoked inhibition of the CA1 distal dendritic excitation, 30-400 ms after the CA3 stimulus. In addition, seizure as compared to control rats showed a reduced early (20-80 ms) inhibition of a CA1 mid-apical dendritic sink following paired-pulse CA3 stimulation. In conclusion, long-term alterations in dendritic inhibition in CA1 were found following early-life seizures.
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Richard Boyce et al.Age FactorsAnimalsDendritesHippocampusHyperthermia, InducedNeural InhibitionRatsRats, Long-EvansRecurrenceSeizuresTime FactorsSeptohippocampal GABAergic neurons mediate the altered behaviors induced by n-methyl-D-aspartate receptor antagonists.http://ir.lib.uwo.ca/physpharmpub/90
http://ir.lib.uwo.ca/physpharmpub/90Fri, 13 Mar 2015 13:37:30 PDT
We hypothesize that selective lesion of the septohippocampal GABAergic neurons suppresses the altered behaviors induced by an N-methyl-D-aspartate (NMDA) receptor antagonist, ketamine or MK-801. In addition, we hypothesize that septohippocampal GABAergic neurons generate an atropine-resistant theta rhythm that coexists with an atropine-sensitive theta rhythm in the hippocampus. Infusion of orexin-saporin (ore-SAP) into the medial septal area decreased parvalbumin-immunoreactive (GABAergic) neurons by ~80%, without significantly affecting choline-acetyltransferase-immunoreactive (cholinergic) neurons. The theta rhythm during walking, or the immobility-associated theta induced by pilocarpine, was not different between ore-SAP and sham-lesion rats. Walking theta was, however, more disrupted by atropine sulfate in ore-SAP than in sham-lesion rats. MK-801 (0.5 mg/kg i.p.) induced hyperlocomotion associated with an increase in frequency, but not power, of the hippocampal theta in both ore-SAP and sham-lesion rats. However, MK-801 induced an increase in 71-100 Hz gamma waves in sham-lesion but not ore-SAP lesion rats. In sham-lesion rats, MK-801 induced an increase in locomotion and an impairment of prepulse inhibition (PPI), and ketamine (3 mg/kg s.c.) induced a loss of gating of hippocampal auditory evoked potentials. MK-801-induced behavioral hyperlocomotion and PPI impairment, and ketamine-induced auditory gating deficit were reduced in ore-SAP rats as compared to sham-lesion rats. During baseline without drugs, locomotion and auditory gating were not different between ore-SAP and sham-lesion rats, and PPI was slightly but significantly increased in ore-SAP as compared with sham lesion rats. It is concluded that septohippocampal GABAergic neurons are important for the expression of hyperactive and psychotic symptoms an enhanced hippocampal gamma activity induced by ketamine and MK-801, and for generating an atropine-resistant theta. Selective suppression of septohippocampal GABAergic activity is suggested to be an effective treatment of some symptoms of schizophrenia.
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Jingyi Ma et al.AnimalsBehavior, AnimalExcitatory Amino Acid AntagonistsGABAergic NeuronsHippocampusMalePsychotic DisordersRatsRats, Long-EvansReceptors, N-Methyl-D-AspartateSeptum of BrainTheta RhythmLong-lasting auditory gating deficit accompanied by GABA(B) receptor dysfunction in the hippocampus after early-life limbic seizures in rats.http://ir.lib.uwo.ca/physpharmpub/89
http://ir.lib.uwo.ca/physpharmpub/89Fri, 13 Mar 2015 13:37:28 PDT
In a previous study, we reported a rat model of early-life limbic seizures which resulted in a loss of GABA(B) receptor inhibition in the hippocampus. Since gating of auditory evoked potentials in the hippocampus (auditory gating) requires GABA(B) receptors and spatial behaviors depend on the hippocampus, we hypothesize that rats with early-life limbic seizures manifest deficits of auditory gating and spatial behaviors. Seizure rats were given a single injection of GABA(B) receptor antagonist CGP56999A (1-1.2 mg/kg i.p.) on postnatal day (PND) 15, which induced multiple limbic seizures in 8h; control rats were given saline injection. When tested at 3-9 weeks after seizure/control treatment, seizure as compared to control rats showed no difference in finding a hidden platform in the water maze, but were deficient in learning and maintaining consecutive criterion performance in the 8-arm radial arm maze. Auditory gating, as measured by paired-click (conditioning followed by test click) average auditory evoked potentials in the hippocampus, revealed a significant difference between seizure rats and controls. Seizure as compared to control rats showed an increased ratio of the test to conditioning click response as adolescents (50 days old) or adults (70 days old). Heterosynaptic electric paired-pulse depression of hippocampal population excitatory postsynaptic potential in freely moving rats, a measure of hippocampal GABA(B)-receptor mediated inhibition, was decreased in seizure as compared to control rats. Seizure as compared to control rats showed increased locomotor activity in a novel open field for the first 10 min, and decreased activity at 15-60 min. However, auditory prepulse inhibition, a measure of sensorimotor gating, revealed no difference between seizure and control rats. In conclusion, early-life limbic seizures induced a long-lasting deficit in auditory gating, likely caused by GABA(B) receptor-mediated inhibition loss in the hippocampus. Auditory gating loss is a symptom of schizophrenia, and thus GABA(B) receptor inhibition loss in the hippocampus provides a mechanism linking early-life seizures to a psychiatric symptom.
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Min-Lan Tsai et al.Acoustic StimulationAnimalsElectric StimulationGABA AntagonistsHippocampusHyperkinesisInjectionsInjections, IntraventricularLimbic EncephalitisLimbic SystemMaleMaze LearningMotor ActivityPhosphinic AcidsRatsRats, Long-EvansReceptors, GABA-BSeizuresSensory GatingStartle ReactionResting-state connectivity identifies distinct functional networks in macaque cingulate cortex.http://ir.lib.uwo.ca/physpharmpub/88
http://ir.lib.uwo.ca/physpharmpub/88Fri, 13 Mar 2015 13:37:25 PDT
Subregions of the cingulate cortex represent prominent intersections in the structural networks of the primate brain. The relevance of the cingulate to the structure and dynamics of large-scale networks ultimately requires a link to functional connectivity. Here, we map fine-grained functional connectivity across the complete extent of the macaque (Macaca fascicularis) cingulate cortex and delineate subdivisions pertaining to distinct identifiable networks. In particular, we identified 4 primary networks representing the functional spectrum of the cingulate: somatomotor, attention-orienting, executive, and limbic. The cingulate nodes of these networks originated from separable subfields along the rostral-to-caudal axis and were characterized by positive and negative correlations of spontaneous blood oxygen level-dependent activity. These findings represent a critical component for understanding how the anterior and midcingulate cortices integrate and shape information processing during task performance. The connectivity patterns also suggest future electrophysiological targets that may reveal new functional representations including those involved in conflict monitoring.
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R Matthew Hutchison et al.AnimalsFemaleGyrus CinguliMacaca fascicularisMagnetic Resonance ImagingMaleNerve NetRestA model of intracellular θ phase precession dependent on intrinsic subthreshold membrane currents.http://ir.lib.uwo.ca/physpharmpub/87
http://ir.lib.uwo.ca/physpharmpub/87Fri, 13 Mar 2015 13:37:23 PDT
A hippocampal place cell fires at an increasingly earlier phase in relation to the extracellular theta rhythm as a rodent moves through the place field. The present report presents a compartment model of a CA1 pyramidal cell that explains the increase in amplitude and the phase precession of intracellular theta oscillations, with the assumption that the cell receives an asymmetric ramp depolarization (<10 >mV) in the place field and rhythmic inhibitory and/or excitatory synaptic driving. Intracellular subthreshold membrane potential oscillations (MPOs) increase in amplitude and frequency, and show phase precession within the place field. Theta phase precession and MPO power and frequency increase in the place field are caused by a shift in excitatory-inhibitory response, intrinsic theta-frequency resonance, and intrinsic oscillations that depend on voltage-dependent persistent Na(+) and slowly inactivating K(+) currents, but not on I(h). Phase precession is diminished when theta-frequency resonance is decreased. Simulated spikes fire near the peak of MPOs and precess similarly as the MPOs. The phase of the MPOs/spikes codes for distance in a one-dimensional place field, and phase precession is only weakly dependent on firing rate, running speed, or the duration needed to cross the place field. In addition, phase precession within the place field resumes quickly after disruption by maximal afferent pulse stimulation.
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L Stan LeungAnimalsCA1 Region, HippocampalComputer SimulationExcitatory Postsynaptic PotentialsInhibitory Postsynaptic PotentialsIntracellular FluidMembrane PotentialsModels, NeurologicalPeriodicityPotassium ChannelsPyramidal CellsRatsSodium ChannelsSynaptic TransmissionTheta RhythmProteomic Signature of the Murine Intervertebral Dischttp://ir.lib.uwo.ca/physpharmpub/86
http://ir.lib.uwo.ca/physpharmpub/86Fri, 13 Mar 2015 13:37:21 PDT
Low back pain is the most common musculoskeletal problem and the single most common cause of disability, often attributed to degeneration of the intervertebral disc. Lack of effective treatment is directly related to our limited understanding of the pathways responsible for maintaining disc health. While transcriptional analysis has permitted initial insights into the biology of the intervertebral disc, complete proteomic characterization is required. We therefore employed liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) protein/peptide separation and mass spectrometric analyses to characterize the protein content of intervertebral discs from skeletally mature wild-type mice. A total of 1360 proteins were identified and categorized using PANTHER. Identified proteins were primarily intracellular/plasma membrane (35%), organelle (30%), macromolecular complex (10%), extracellular region (9%). Molecular function categorization resulted in three distinct categories: catalytic activity (33%), binding (molecule interactions) (29%), and structural activity (13%). To validate our list, we confirmed the presence of 14 of 20 previously identified IVD-associated markers, including matrix proteins, transcriptional regulators, and secreted proteins. Immunohistochemical analysis confirmed distinct localization patterns of select protein with the intervertebral disc. Characterization of the protein composition of healthy intervertebral disc tissue is an important first step in identifying cellular processes and pathways disrupted during aging or disease progression.
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Matthew R. McCannActivation of immobility-related hippocampal theta by cholinergic septohippocampal neurons during vestibular stimulation.http://ir.lib.uwo.ca/physpharmpub/85
http://ir.lib.uwo.ca/physpharmpub/85Fri, 13 Mar 2015 13:11:24 PDT
The vestibular system has been suggested to participate in spatial navigation, a function ascribed to the hippocampus. Vestibular stimulation during spatial navigation activates a hippocampal theta rhythm (4-10 Hz), which may enhance spatial processing and motor response. We hypothesize that a cholinergic, atropine-sensitive theta is generated during passive whole-body rotation in freely behaving rats. Hippocampal EEGs were recorded by implanted electrodes in CA1 while rats were rotated on a vertical axis, for a minute or longer, at different angular velocities. Rotation induced a continuous hippocampal theta rhythm while the rat was immobile, in both light and dark conditions. Theta peak frequency showed a significant increase during high (50-70 rpm) as compared with a lower (20-49 rpm) rotational velocity. Rotation-induced theta was abolished by muscarinic receptor antagonist atropine sulfate (50 mg/kg i.p.) but not by atropine methyl nitrate (50 mg/kg i.p.), which did not pass the blood-brain barrier. Theta was attenuated in rats in which cholinergic neurons in the medial septum (MS) were lesioned with 192 IgG-saporin (0.14 μg in 0.4 μl), as confirmed by depletion of MS cells immunoreactive to choline acetyltransferase and an absence of acetylcholinesterase staining in the hippocampus. Bilateral lesion of the vestibular receptors by sodium arsanilate (30 mg in 0.1 ml, intratympanically) also attenuated the rotation-induced theta rhythm. In intact rats, field excitatory postsynaptic potentials (fEPSPs) in CA1 evoked by commissural stimulation were smaller during walking or rotation as compared with during immobility. Modulation of fEPSP was absent following atropine sulfate in intact rats and in 192 IgG-saporin lesion rats. In summary, this is the first report of a continuous atropine-sensitive hippocampal theta in the rat induced by vestibular stimulation during rotation, and accompanied by cholinergic modulation of hippocampal synaptic transmission. Vestibular-activated septohippocampal cholinergic activity could be an important component in sensorimotor processing and spatial memory.
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Siew Kian Tai et al.AnimalsAntibodies, MonoclonalAtropineAtropine DerivativesBlood-Brain BarrierCholine O-AcetyltransferaseCholinergic NeuronsElectric StimulationExcitatory Postsynaptic PotentialsHippocampusImmobilizationImmunotoxinsMaleMuscarinic AntagonistsRatsRats, Long-EvansRibosome Inactivating Proteins, Type 1RotationTheta RhythmVestibule, LabyrinthWalkingTracing notochord-derived cells using a Noto-cre mouse: implications for intervertebral disc development.http://ir.lib.uwo.ca/physpharmpub/83
http://ir.lib.uwo.ca/physpharmpub/83Fri, 03 May 2013 09:20:49 PDT
Back pain related to intervertebral disc degeneration is the most common musculoskeletal problem, with a lifetime prevalence of 82%. The lack of effective treatment for this widespread problem is directly related to our limited understanding of disc development, maintenance and degeneration. The aim of this study was to determine the developmental origins of nucleus pulposus cells within the intervertebral disc using a novel notochord-specific Cre mouse. To trace the fate of notochordal cells within the intervertebral disc, we derived a notochord-specific Cre mouse line by targeting the homeobox gene Noto. Expression of this gene is restricted to the node and the posterior notochord during gastrulation [embryonic day 7.5 (E7.5)-E12.5]. The Noto-cre mice were crossed with a conditional lacZ reporter for visualization of notochord fate in whole-mount embryos. We performed lineage-tracing experiments to examine the contribution of the notochord to spinal development from E12.5 through to skeletally mature mice (9 months). Fate mapping studies demonstrated that, following elongation and formation of the primitive axial skeleton, the notochord gives rise to the nucleus pulposus in fully formed intervertebral discs. Cellular localization of β-galactosidase (encoded by lacZ) and cytokeratin-8 demonstrated that both notochordal cells and chondrocyte-like nucleus pulposus cells are derived from the embryonic notochord. These studies establish conclusively that notochordal cells act as embryonic precursors to all cells found within the nucleus pulposus of the mature intervertebral disc. This suggests that notochordal cells might serve as tissue-specific progenitor cells within the disc and establishes the Noto-cre mouse as a unique tool to interrogate the contribution of notochordal cells to both intervertebral disc development and disc degeneration.
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Matthew R McCann et al.AnimalsEmbryo, MammalianIntegrasesIntervertebral DiscKeratin-8MiceNotochordOsteogenesisStaining and LabelingTime Factorsbeta-GalactosidaseAcute Vibration Induces Transient Expression of Anabolic Genes in the Murine Intervertebral Dischttp://ir.lib.uwo.ca/physpharmpub/82
http://ir.lib.uwo.ca/physpharmpub/82Thu, 02 May 2013 13:15:51 PDTMatthew R. McCann et al.One- and three-dimensional growth of hydroxyapatite nanowires during sol-gel-hydrothermal synthesis.http://ir.lib.uwo.ca/physpharmpub/81
http://ir.lib.uwo.ca/physpharmpub/81Tue, 30 Oct 2012 05:26:13 PDT
Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol-gel-hydrothermal process. Sol-gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol-gel-hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10-50 wt %) were mixed with poly(ε-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young's and compressive moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA producing a 3-fold increase in Young's modulus from 193 to 665 MPa and 2-fold increase in compressive modulus from 230 to 487 MPa. These HA nanowires can be used to reinforce polymer composites and are excellent biomaterials for tissue engineering of bone.
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Daniel O Costa et al.Calcium PhosphatesCompressive StrengthDurapatiteGelsHydrogen-Ion ConcentrationMaterials TestingNanoparticlesNanotechnologyNanowiresParticle SizePhase TransitionPolyestersPowdersSpectroscopy, Fourier Transform InfraredTemperatureTensile StrengthWaterX-Ray DiffractionControl of surface topography in biomimetic calcium phosphate coatings.http://ir.lib.uwo.ca/physpharmpub/80
http://ir.lib.uwo.ca/physpharmpub/80Tue, 30 Oct 2012 05:26:11 PDT
The behavior of cells responsible for bone formation, osseointegration, and bone bonding in vivo are governed by both the surface chemistry and topography of scaffold matrices. Bone-like apatite coatings represent a promising method to improve the osteoconductivity and bonding of synthetic scaffold materials to mineralized tissues for regenerative procedures in orthopedics and dentistry. Polycaprolactone (PCL) films were coated with calcium phosphates (CaP) by incubation in simulated body fluid (SBF). We investigated the effect of SBF ion concentration and soaking time on the surface properties of the resulting apatite coatings. CaP coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and energy dispersive X-ray spectrometry (EDX). Young's modulus (E(s)) was determined by nanoindentation, and surface roughness was assessed by atomic force microscopy (AFM) and mechanical stylus profilometry. CaP such as carbonate-substituted apatite were deposited onto PCL films. SEM and AFM images of the apatite coatings revealed an increase in topographical complexity and surface roughness with increasing ion concentration of SBF solutions. Young's moduli (E(s)) of various CaP coatings were not significantly different, regardless of the CaP phase or surface roughness. Thus, SBF with high ion concentrations may be used to coat synthetic polymers with CaP layers of different surface topography and roughness to improve the osteoconductivity and bone-bonding ability of the scaffold.
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Daniel O Costa et al.Biocompatible MaterialsBiomimeticsCalcium PhosphatesCoated Materials, BiocompatibleElastic ModulusMicroscopy, Electron, ScanningPolyestersSpectrometry, X-Ray EmissionSurface PropertiesX-Ray DiffractionP2X₇-mediated calcium influx triggers a sustained, PI3K-dependent increase in metabolic acid production by osteoblast-like cells.http://ir.lib.uwo.ca/physpharmpub/79
http://ir.lib.uwo.ca/physpharmpub/79Tue, 30 Oct 2012 05:26:06 PDT
The P2X₇ receptor is an ATP-gated cation channel expressed by a number of cell types, including osteoblasts. Genetically modified mice with loss of P2X₇ function exhibit altered bone formation. Moreover, activation of P2X₇ in vitro stimulates osteoblast differentiation and matrix mineralization, although the underlying mechanisms remain unclear. Because osteogenesis is associated with enhanced cellular metabolism, our goal was to characterize the effects of nucleotides on metabolic acid production (proton efflux) by osteoblasts. The P2X₇ agonist 2',3'-O-(4-benzoylbenzoyl)ATP (BzATP; 300 μM) induced dynamic membrane blebbing in MC3T3-E1 osteoblast-like cells (consistent with activation of P2X₇ receptors) but did not induce cell death. Using a Cytosensor microphysiometer, we found that 9-min exposure to BzATP (300 μM) caused a dramatic increase in proton efflux from MC3T3-E1 cells (∼2-fold), which was sustained for at least 1 h. In contrast, ATP or UTP (100 μM), which activate P2 receptors other than P2X₇, failed to elicit a sustained increase in proton efflux. Specific P2X₇ receptor antagonists A 438079 and A 740003 inhibited the sustained phase of the BzATP-induced response. Extracellular Ca²⁺ was required during P2X₇ receptor stimulation for initiation of sustained proton efflux, and removal of extracellular glucose within the sustained phase abolished the elevation elicited by BzATP. In addition, inhibition of phosphatidylinositol 3-kinase blocked the maintenance but not initiation of the sustained phase. Taken together, we conclude that brief activation of P2X₇ receptors on osteoblast-like cells triggers a dramatic, Ca²⁺-dependent stimulation of metabolic acid production. This increase in proton efflux is sustained and dependent on glucose and phosphatidylinositol 3-kinase activity.
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Matthew W Grol et al.Adenosine TriphosphateAnimalsBone RemodelingCalcium SignalingCell LineCell SurvivalClone CellsEnzyme InhibitorsGlucoseHydrogen-Ion ConcentrationKineticsLactic AcidLigandsMiceOsteoblastsPhosphatidylinositol 3-KinasesPurinergic P2X Receptor AgonistsPurinergic P2X Receptor AntagonistsReceptors, Purinergic P2X7Uridine TriphosphateVisualization of the solubilization process of the plasma membrane of a living cell by waveguide evanescent field fluorescence microscopy.http://ir.lib.uwo.ca/physpharmpub/78
http://ir.lib.uwo.ca/physpharmpub/78Tue, 30 Oct 2012 05:06:03 PDT
Waveguide evanescent field fluorescence microscopy (WEFF) is a novel microscopy technology that allows imaging of a cell's plasma membrane in the vicinity of a glass substrate with high axial resolution, low background and little photobleaching. Time-lapse imaging can be performed to investigate changes in cell morphology in the presence or absence of chemical agents. WEFF microscopy provides a method to investigate plasma membranes of living cells and allows a comparison to simplified model membranes immobilized on planar substrates. The interaction of the nonionic detergent Triton X-100 with plasma membranes of osteoblasts in an aqueous environment was investigated. Solubilization of the membranes very close to the waveguide surface was visualized and related to the three-stage solubilisation model proposed for liposomes and supported lipid bilayers. Findings for the plasma membranes of cells are in excellent agreement with results reported for these artificial model systems.
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Abdollah Hassanzadeh et al.One- and three-dimensional growth of hydroxyapatite nanowires during sol-gel-hydrothermal synthesis.http://ir.lib.uwo.ca/physpharmpub/77
http://ir.lib.uwo.ca/physpharmpub/77Mon, 29 Oct 2012 05:10:51 PDT
Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol-gel-hydrothermal process. Sol-gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol-gel-hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10-50 wt %) were mixed with poly(ε-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young's and compressive moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA producing a 3-fold increase in Young's modulus from 193 to 665 MPa and 2-fold increase in compressive modulus from 230 to 487 MPa. These HA nanowires can be used to reinforce polymer composites and are excellent biomaterials for tissue engineering of bone.
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Daniel O Costa et al.Calcium PhosphatesCompressive StrengthDurapatiteGelsHydrogen-Ion ConcentrationMaterials TestingNanoparticlesNanotechnologyNanowiresParticle SizePhase TransitionPolyestersPowdersSpectroscopy, Fourier Transform InfraredTemperatureTensile StrengthWaterX-Ray DiffractionControl of surface topography in biomimetic calcium phosphate coatings.http://ir.lib.uwo.ca/physpharmpub/76
http://ir.lib.uwo.ca/physpharmpub/76Mon, 29 Oct 2012 05:05:46 PDT
The behavior of cells responsible for bone formation, osseointegration, and bone bonding in vivo are governed by both the surface chemistry and topography of scaffold matrices. Bone-like apatite coatings represent a promising method to improve the osteoconductivity and bonding of synthetic scaffold materials to mineralized tissues for regenerative procedures in orthopedics and dentistry. Polycaprolactone (PCL) films were coated with calcium phosphates (CaP) by incubation in simulated body fluid (SBF). We investigated the effect of SBF ion concentration and soaking time on the surface properties of the resulting apatite coatings. CaP coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and energy dispersive X-ray spectrometry (EDX). Young's modulus (E(s)) was determined by nanoindentation, and surface roughness was assessed by atomic force microscopy (AFM) and mechanical stylus profilometry. CaP such as carbonate-substituted apatite were deposited onto PCL films. SEM and AFM images of the apatite coatings revealed an increase in topographical complexity and surface roughness with increasing ion concentration of SBF solutions. Young's moduli (E(s)) of various CaP coatings were not significantly different, regardless of the CaP phase or surface roughness. Thus, SBF with high ion concentrations may be used to coat synthetic polymers with CaP layers of different surface topography and roughness to improve the osteoconductivity and bone-bonding ability of the scaffold.
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Daniel O Costa et al.Biocompatible MaterialsBiomimeticsCalcium PhosphatesCoated Materials, BiocompatibleElastic ModulusMicroscopy, Electron, ScanningPolyestersSpectrometry, X-Ray EmissionSurface PropertiesX-Ray Diffraction